Moses was unable to enter the Tent of Meeting because the cloud had settled on it, and the glory of the LORD filled the tabernacle.

Numbers 7:89
When Moses entered the Tent of Meeting to speak with the LORD, he heard the voice speaking to him from between the two cherubim above the mercy seat on the ark of the Testimony. Thus the LORD spoke to him.

1 Kings 8:10
And when the priests came out of the Holy Place, the cloud filled the house of the LORD

1 Kings 8:11
so that the priests could not stand there to minister because of the cloud; for the glory of the LORD filled the house of the LORD.

2 Chronicles 5:13
The trumpeters and singers joined together to praise and thank the LORD with one voice. They lifted up their voices, accompanied by trumpets, cymbals, and musical instruments, in praise to the LORD: "For He is good; His loving devotion endures forever." And the temple, the house of the LORD, was filled with a cloud

2 Chronicles 5:14
so that the priests could not stand there to minister because of the cloud; for the glory of the LORD filled the house of God.

Ezekiel 10:4
Then the glory of the LORD rose from above the cherubim and stood over the threshold of the temple. The temple was filled with the cloud, and the court was filled with the brightness of the glory of the LORD.

And Moses was not able to enter into the tent of the congregation, because the cloud stayed thereon, and the glory of the LORD filled the tabernacle.